Is biology considered a predictive science

3 THE SIMPLICITY AND COMPLEXITY OF LIFE As I mentioned in the first chapter, living systems - from the smallest bacteria to the largest cities and ecosystems - are complex adaptive systems that differ in their size and thus their weight, in their lifespan and differ in their energy requirements by many orders of magnitude. In terms of weight alone, the spectrum of life - from the molecules that supply the metabolism with energy to ecosystems and cities - covers more than 30 orders of magnitude (1030). This range is far greater than that between the weight of the earth and that of the Milky Way, which is “only” 18 orders of magnitude and the range between the weight of an electron and that of a mouse is comparable. In this vast spectrum, life essentially makes use of the same elementary building blocks and processes over and over again to create an incredible variety of forms, functions and dynamic behaviors - clear evidence of the power of natural selection and evolutionary dynamics. All life is based on converting the energy obtained from physical or chemical sources into organic molecules, which in turn are converted to form, maintain and reproduce complex, highly organized systems. This is achieved through the interaction of two systems: the genetic code, which contains and processes the information and "instructions" necessary for the construction and maintenance of the organism, and the metabolic system, which provides the energy and raw materials for maintenance, growth and the Reproduction of the organism procures, transforms and distributes. We have made great strides in understanding both systems, from the molecular to the organism level, THE SIMPLICITY AND COMPLEXITY OF LIFE, 90 and I will later explain how these advances can be extended to cities and businesses. However, it is still not understood how the processing of information («genomics») is combined with the processing of energy and raw materials («metabolism») and thus sustains life. Understanding the general principles underlying the structures, dynamics and interplay of these systems is essential for understanding what life is and for dealing with biological and socio-economic systems in contexts as diverse as medicine, agriculture and indispensable for the environment. A holistic approach to understanding genetics has already been developed that can explain phenomena ranging from the replication, transcription and translation of genes to the evolutionary origin of species. What is still missing is a comparable holistic theory of metabolism. It would have to combine the processes by which the processes of converting energy and raw materials, which consist of biochemical reactions in the cells, are upscaled in order to enable life, to supply biological activities with energy and the time frame for vital processes from the level of the organisms up to that of the ecosystems. The search for the basic principles that allow the complexity of life to emerge from the simplicity on which it is based is one of the great challenges facing science in the 21st century. Biologists and chemists will continue to be primarily responsible for this, but other disciplines, especially physics and computer science, play a role in The Extraordinary Range of Life, from complex molecules and microbes to whales, compared to subatomic and galactic orders of magnitude . 10 −30 kg electron 10 42 kg M ilchstrasse 10 36 kg black hole 10 30 kg sun 10 −27 kg hydrogen atom Cytochrome oxidase of the respiratory chain 10 −22 kg mycoplasma mitochondrium 10 −16 kg 10 −13 kg bacterium 10 −11 kg cell 10 −7 kg am öbe 10 −4 kg bee 10 −3 kg pointed m from 1 kg 10 2 kg human 10 5 kg whale 10 24 kg earth Fig. 8 The simplicity and complexity of life 91 of this search an increasingly important role. A thorough understanding of the emergence of complexity out of simplicity is one of the challenges that have led to the development of the new complexity science. Physics deals with basic principles and concepts (on all organizational levels) that are quantifiable and mathematical (that is, calculable) and therefore allow the establishment of precise predictions that can be verified by experiment and observation. In this respect, the question arises as to whether there are mathematical “universal laws of life”, which would mean that biology, like physics, could be formulated as a predictive, quantifying science. Is it conceivable that there are yet to be discovered “Newton's laws of biology” which, at least in principle, would enable precise calculations of all biological processes so that, for example, one could predict exactly how long you and I will live? It is very unlikely. After all, life is the complex system par excellence, with many levels, the phenomena of which have emerged in very different, always random strands of development history. Nevertheless, it is perhaps not unreasonable to assume that the behavior of living systems, viewed from a certain distance, obeys quantifiable general laws that determine their essential properties. This more modest perspective assumes that ideal-typical average biological systems can be constructed at every organizational level, the general properties of which can be calculated. This is how we should be able to calculate the average and maximum life expectancy of people, even if we will never be able to predict our own. That would be a starting point or a basis for a quantifying understanding of actually existing biosystems, which, arising from local environmental conditions or evolutionary-historical branches, can be viewed as deviations from ideal-typical norms. I will delve into this perspective much more deeply as it forms the conceptual strategy for answering most of the questions I raised in the first chapter. THE SIMPLICITY AND COMPLEXITY OF LIFE 92 1. FROM QUARKS AND STRINGS TO CELLS AND WHALE Before I dive into discussing some of those big questions, let me tell you briefly of the fortunate circumstances that make me think about the fundamental questions of physics have also led to fundamental questions of biology and finally also of the socio-economic sciences, which are of importance for central questions relating to global sustainability. In October 1993, with the approval of President Clinton, the United States Congress officially halted the largest scientific project of all time: the construction of the gigantic Superconducting Super Collider (SSC), which by then had devoured nearly $ 3 billion. The SSC, a particle accelerator, the development of which, together with that of its detectors, represented the greatest technical challenge that had ever been tackled. As a giant “microscope”, it should have examined lengths down to a hundred billionths of a micron in order to determine structure and To reveal the dynamics of the basic building blocks of matter. With it it would have been possible to test predictions derived from the theory of elementary particles, perhaps also to discover new phenomena and to lay the foundations for the so-called "great holistic theory" of all fundamental forces of nature. The great vision would not only have given us the knowledge of what all compound phenomena consist of, but it would also have given us essential insights into the development of the universe from the Big Bang on. In many ways, it represented one of man's greatest desires as the only creature with sufficient intelligence to face the never-ending challenge of unraveling some of the greatest mysteries in the universe. And who knows, maybe this is the reason we humans exist as the agents through which the universe recognizes itself. The SSC had a circumference of more than 80 kilometers and was supposed to accelerate protons up to energies of 20 trillion electron volts for more than 10 billion dollars. To give an impression of the order of magnitude: An electron volt is the average energy with which the chemical reactions that form the basis of life take place. The energy of the protons in the SSC would have been eight times that of the Great Hadron Storage Ring, From Quarks and Strings to Cells and Whales 93 which is now in operation in Geneva and was recently in the limelight because the Higgs particle was discovered in it. The end of the SSC had many almost predictable causes, including inevitable budget problems, the state of the economy, political resentment against Texas, where the machine was under construction, and uninspired leadership. One of the main reasons, however, was the emergence of a climate of rejection of traditional great science, especially physics, 1 which was articulated in many ways, including the oft-repeated assertion I have already quoted that the 21st century will be the century of Be biology after the 20th century was physics. Now even the most arrogant, die-hard physicist cannot deny the feeling that biology is likely to dwarf physics as the dominant science of the 21st century. But what upset many of us was the implication, often explicitly expressed, that there was no longer any need for further basic research in physics because we already knew everything that had to be known. Unfortunately, the SSC was a victim of this foolish, provincial mindset. I was leading the high energy physics program in Los Alamos at the time, and we had been very involved in the development of one of the two large detectors being built at the SSC. For those who are not familiar with the terminology: "High-energy physics" is the name of the branch of physics that deals with fundamental questions concerning elementary particles, their interactions and cosmological implications. My primary research interests in theoretical physics were (and still are) in this area. My intuitive reaction to the provocative remarks about the future of physics and biology was that, indeed, biology will almost certainly be the dominant science of the 21st century, but that to be truly successful it will be something of the quantifying, analytical, predictive culture that has made physics so successful. With its traditional reliance on statistical, phenomenological and qualifying argumentation, biology will have to combine a more theoretical approach based on mathematical principles. I am embarrassed to say that I knew very little about biology at the time, and that the strange reasoning quoted was largely based on arrogance and ignorance. Still, I made up my mind to do something, and began to think about how the SIMPLICITY AND COMPLEXITY OF LIFE94 mindset of physics could help solve interesting problems in biology. Of course, there had already been extremely successful excursions by physicists into biology: the most spectacular was that of Francis Crick, who had helped James Watson to fathom the structure of DNA and thus to revolutionize our understanding of the genome. Another example was the wonderful little book What Is Life? the eminent physicist and co-founder of quantum mechanics, Erwin Schrödinger, who had a great influence on biology.2 These examples, inspirational evidence that physics could have something interesting to say to biology, had encouraged a small but growing group of physicists to to bridge the divide and to contribute to the development of biophysics. I was in my early fifties when the SSC came to an end and, as I mentioned at the beginning, I became more and more aware of the inevitable impairments of the aging process and the resulting finiteness of life. Given the poor track record of growing old men among my ancestors, it made sense that I began my biology thinking with a desire to learn about aging and dying. Since these phenomena are among the most widespread and fundamental "processes" in life, I naively assumed that they had been researched more or less exhaustively. But to my great surprise I learned that not only was there no generally accepted theory of aging and dying, but that little had been done in this area of ​​research. Few of the questions that would be the most natural thing in the world for a physicist to ask; questions like those I raised in the first chapter seemed to have caught the interest of researchers. This was especially true for these two: Where does the order of magnitude of a hundred years of human life expectancy come from? And: what would a quantifying, predictive theory of aging consist of? Dying is an integral part of life. Yes, implicitly, it is even an essential part of evolution, because it is necessary for the evolutionary process that individuals die at some point so that their offspring can spread new combinations of genes that ultimately lead to the adaptation of new traits through natural selection and enlargement the diversity of species. We all have to die for the new to flourish, explore the world, adapt and evolve. Steve Jobs put this thought succinctly: From quarks and strings to cells and whales 95 Nobody wants to die. Even people who wish to get to heaven don't want to die to get there. Nevertheless: death is the goal of all of us. Nobody has ever escaped it, and that's a good thing, because death is probably by far the best invention of life. He is the catalyst of change. He discards the old to make way for the new.3 Because of the great importance of death and its precursor, the aging process, I had assumed that an entire chapter in an introduction to biology would be devoted to both phenomena would, just as such a book is devoted to the other elementary things in life - birth, growth, reproduction, metabolism, and so on. I was expecting the didactic summary of a mechanistic theory of aging, with a simple calculation of why we can live to be about a hundred years old, and with answers to all of the questions I asked above. But nothing like that! These things were not even mentioned and there was nothing to suggest that they were of any interest. That was a surprise, especially since death after birth is the most dramatic biological event in a person's life. As a physicist, I began to wonder to what extent biology was a "real" science (by which I meant, of course, how much it was like physics!) And how it would dominate the 21st century when dealing with such fundamental questions not concerned. This apparent lack of scientific interest on the part of biologists in aging and death, apart from a relatively small number of dedicated researchers, spurred me to ponder these questions. Since it appears as good as no one has tackled them quantitatively or analytically, a physical approach might be able to provide a small step forward. So when I wasn't dealing with quarks, gluons, dark matter, and string theory, I started thinking about death in the form of pause fillers. When I set out, I received confirmation from an unexpected source of my ruminations about biology as a science and its relationship to mathematics. I discovered that the eminent, somewhat eccentric biologist Sir D'Arcy Wentworth Thompson had expressed my supposedly subversive thoughts much better and more profoundly in his classic work On Growth and Form, published in 1917.4 The book is THE SIMPLICITY AND COMPLEXITY DES LEBENS96 wonderful and is held in honor not only by biologists, but also by mathematicians, visual artists and architects. It has influenced thinkers and artists, from Alan Turing and Julian Huxley to Jackson Pollock. Evidence of its unbroken popularity is the fact that it is still available.The famous biologist Sir Peter Medawar, the father of organ transplants, who was awarded the Nobel Prize for his work on transplant rejection and acquired immune tolerance, has named On Growth and Form "the most beautiful literary work in English in the annals of science." D'Arcy Wentworth Thompson, offspring of a Scottish intellectual family and, like Isambard Kingdom Brunel, the bearer of a name that would be associated with a minor character in a Victorian novel, was one of the last of the "Renaissance men": representative of a species of multi- and transdisciplinary scientists-scholars as they hardly exist today. Although his greatest influence was on biology, he was also a highly qualified classical philologist and mathematician. He was elected President of the British Classical Association, President of the Royal Geographical Society and, as a mathematician, competent enough to become an honorary member of the prestigious Edinburgh Mathematical Society. Thompson opens his book with a word from Immanuel Kant, who had said that the chemistry of his time was "a science, but not a science," which Thompson interprets to mean that "the criterion of real science is based on its relationship to mathematics." Thompson argued that there is now a scientific, principle-based predictive “mathematical chemistry”. In contrast, biology is still only "a science", namely purely qualifying, without mathematical foundations or principles. It would only rise to "science" in the emphatic Kantian sense if it made mathematical physical principles its own. I realized that Thompson's provocative characterization of biology, despite the extraordinary advances the science had made since then, was still somewhat justified. The fact that the Royal Society awarded him the coveted Darwin Medal in 1946 should not hide the fact that Thompson was critical of conventional Darwinian evolution because he felt that biologists understood the importance of natural selection and “over - From quarks and strings to cells and whales 97 of the best adapted »as the determinants decisive for the form and structure of living organisms overestimated and underestimated the importance of physical laws that can be formulated mathematically. The fundamental question contained in Thompson's doubts about biology as a science remains unanswered: Are there mathematical “universal laws of life” on the basis of which biology could be formulated as a predictive, quantifying science? Thompson put it this way: We do well to keep in mind that it took great men in physics to discover simple things. [...] Nobody can predict how far [...] mathematics will suffice to describe the structure of our body and physics to explain it. It may be that all the laws of energy and all the properties of matter and the whole chemistry of colloids are just as incapable of explaining the body as they are of making the essence of the soul comprehensible. I don't think so myself. Physical science does not teach me how it comes that the soul directs the body, and that living matter influences and is influenced by the mind is an unsolved mystery. Consciousness is not explained to me through all of the physiologist's nerve lines and neurons; Nor do I ask physics to explain why goodness shines in one person's face and evil reveals itself in another. But with regard to the structure, growth and function of the body, as for everything physically earthly, physical science is our only teacher and guide in my inconclusive opinion.6 These sentences express the creed of modern "complexity science" well, especially they do implicitly also say that consciousness is an emergent systemic phenomenon and does not simply result from the sum of all “nerve conductors and neurons” in the brain. The book is written in a scientific but perfectly readable style that requires surprisingly little math. Thompson does not preach great principles, but only expresses the conviction that primarily the mathematically formulated physical laws of nature determine the growth and form of individuals as well as the evolution of species as biological phenomena. Although the book neither deals with aging and dying nor is technically demanding, so that it was not particularly helpful for me in concrete terms, I found confirmation and inspiration for my thinking in its philosophy THE SIMPLICITY AND COMPLEXITY OF LIFE98 about physical ideas and methods and for their transfer to all possible problems of biology. I now viewed the human body as a metaphorical machine that needs power, maintenance, and repair, but wears out over time and, like a car or a washing machine, eventually "dies". But in order to understand how something ages and dies, be it an animal, a car, a company or a civilization, one must first understand which processes and mechanisms keep this something alive, and then find out how these processes and mechanisms are after and then lose performance. Of course, this entails considerations about the energy and raw materials required for maintenance and possibly growth, and their distribution for maintenance and repair purposes in order to minimize wear and tear, defects, decay and so on and thus the production of entropy. This train of thought moved me to first work out the central importance of metabolism for our life, and then to ask why it cannot keep us alive for all eternity. 2. METABOLISM RATE AND NATURAL SELECTION Metabolism is the fire of life, food is the fuel of life. Neither the neurons in your brain nor the molecules in your genes could do their job if they weren't supplied with metabolic energy extracted from your food. Without metabolic energy you could not walk, think, or even sleep. The metabolism provides the energy that organisms need for maintenance, growth and reproduction, and thus also for special processes such as muscle contractions, blood circulation and nerve conduction. The metabolic rate is the fundamental speed of biology, as it determines how fast almost all functions of an organism take place - from the biochemical reactions in the cells to the time it takes for the organism to mature to the carbon dioxide uptake of a forest up to the rate at which its foliage crumbles. As already mentioned in the first chapter, the basal metabolic rate of humans is on average only about 90 watts, which corresponds to the power consumption of a conventional light bulb and the approximately 2000 calories that we have to eat at least every day.